Scientists have identified five major phases of brain development across the human lifespan, with key transitions occurring around the ages of 9, 32, 66 and 83, according to a large new study.
Researchers analysed brain scans from nearly 4,000 people ranging from infancy to 90 years old. They found that brain development does not follow a smooth, gradual path, but instead shifts through clear “epochs” marked by major changes in neural organisation.
The five phases identified were:
- Childhood: from birth to around age 9
- Adolescence: from about 9 to 32
- Adulthood: beginning around age 32 and lasting for more than 30 years
- Early ageing: starting around age 66
- Late ageing: beginning around age 83
During childhood, the brain undergoes “network consolidation”, where excess neural connections are trimmed and more active pathways are strengthened. In adolescence, white matter continues to grow and brain networks become more efficient, supporting improved cognitive function.
The most significant shift happens around the early 30s, when the brain enters a more stable “adult” mode. This phase is linked with more compartmentalised brain regions and a relative plateau in intelligence and personality traits compared with earlier life.
Later in life, from the mid-60s onwards, the study observed reductions in brain connectivity, which researchers believe are linked to ageing and white matter degeneration.
Scientists say these findings could help pinpoint periods when the brain is most vulnerable to disruption and may offer new insights into the timing of mental health conditions and age-related cognitive decline.
